Mention llvm-ffi/llvm-tf at Hackage

[amigalemming]

Currently, the hackage package pages http://hackage.haskell.org/package/llvm-base and http://hackage.haskell.org/package/llvm suggest that you should transition to the llvm-general project, which also seems to stall at LLVM-3.5. Could you please also mention my forks? llvm-ffi replaces llvm-base and llvm-tf replaces llvm. It might be easier for people to transition to these packages instead of llvm-general.